1. Field of the Invention
The present invention relates to an air-fuel ratio controller for carburetors and, more particularly, to an air-fuel ratio controller for carburetors, incorporating an electronic controlling means capable of optimizing the air-fuel ratio of the air-fuel mixture supplied from the carburetor to an internal combustion engine in either one or both of warming up after cold start and deceleration of the engine.
2. Description of the Prior Art
In the conventional carburetors, the control of air-fuel ratio supplied to the engine during warming up after a cold start of the engine has been made by a heat sensitive member such as a bimetal operatively connected to the choke valve of the carburetor.
This controlling system, however, cannot provide a sufficiently high precision of the air-fuel ratio control, because the controlling operation is made fully mechanically. In addition, the construction of the carburetor is complicated to cause various troubles.
Also, in the conventional carburetors, a vacuum-sensitive valve generally referred to as "coasting richer" is used for controlling the air-fuel ratio of the mixture during deceleration of the engine through controlling the degree of opening of the fuel passage opening to the downstream side of throttle valve of the carburetor.
This system also fails to provide a sufficiently high precision of air-fuel ratio control because it fully relies upon mechanical operation.